larsson



July 5, 1932. K. LARSSON TELEPHONE SYSTEM Filed Feb. 25, 1 30 s Sheets-Sheet 1 July 5, 1932. K. L'ARSSON 1,865,699

TELEPHONE SYSTEM Filed Feb. 25, 1930 5 ShGBtS-Sheet 2 A4 05mm K. LARSSON TELEPHONE SYSTEM July 5, 1932.

s Sheets-Shet 5 Filed Feb. 25, 1930 .uvveNTdlg [32 l W s Patented July 5, 1932 warren sra'res ATENT OFFICE KNUT LARSSON, OF STOCKHOLM, SWEDEN, ASSIGNOR TO TELEFONAKTIEBOLAGET L. M.

SW'EDEN, A COMPANY OF SWEDEN ERICSSON, 0F STQCKHOLM,

TELEPHONE SYSTEM Application filed February 25, 1930, Serial No. 431,278, and in Sweden February 28, 1929.

matic telephone plants where the call receivers are constituted by registers in which the wanted subscribers number is registered and which serve to control the setting of the selectors. In such systems the call receivers have hitherto been adapted to be connected by means of so called register finders or cord finders to each of the junction lines or cord 7 lines available for a group of subscribers lines in common. The researches upon which the present invention is based have shown that the number of connection possibilities in such register finders or cord finders is unnecessarily great in comparison with the requirements determined for a certain trafiic frequency through the calculus of probabilities. The present invention has for its object to utilize the results of said research in order to simplify and cheapen the switching arrangements required for the connection of the call receivers to the junction lines. The invention is substantially characterized in that the call receivers appertaining to a group of calling lines are distributed among the junction lines belonging to the same line group in such a manner that each call receiver may be associated only with a limited number of said junction lines.

The invention is not restricted to systems having registers but may be applied also in other systems having call receivers, by way of example such manual or semi-automatic systems in which the wanted number is registered and made visible for the operator on a call indicator or the like.

The invention will be more closely described with re'ference to the accompanying drawings. Figure 1 shows diagrammatically a known arrangement adapted to connect call receivers to junction lines, whereas Figures 2 to 5 show different embodiments according to the invention. Figure 6 shows a circuit diagram for an embodiment according to Figure 4;. r

In Figure 1, G designates a group of junction lines or cord lines F which are available for a group of subscribers lines in common. In the shown example each such unction line is provided with a call finder S through which the junction line may be connected to any one of the subscribers lines belonging to the same subscribers group and also to a selector V which may be a group selector or a final selector and through which the talking connect-ion may be extended in known manner. To the same subscribers group a number of call receivers R, such as registers, are allotted which registers are available for all subscribers lines in common in the group as each call receiver over an appertaining line E may be connected to any one of said junction lines F. The possibilities of connection are indicated on the drawings'by means of small circles in the points of intersection between the lines E and F. In the shown example it is assumed hat the subscribers group comprises five hundred subscribers lines, thirty two junction lines F and seven call finders R. The connection of a call receiver to a junction line may take place by means of switching apparatus of arbitrary kind, such as register finders allotted to the different junction lines, or cord finders allotted to the different call receivers.

Figure 2 shows an arrangement according to the invention for the same subscribers group having the same number of junction lines and call receivers. According to this embodiment the junction lines are divided in a number of sub-groupseach allotted to their special call receiver. Each call receiver has thus no longer any possibility, as in Figure 1, to be connected to all the junction lines in the group but the junction lines are distributed among the different call receivers in such a manner that each call receiver may be connected only to a limited number of junction lines. The call receiver-R has thus access only to the five first junction lines, the call receiver R only to the five following junction lines, etc. the system being preterably arranged in such a way that the different call receivers are allotted to an equal or nearly equal number of junction lines. Due to the fact that the different call receivers are uniformly distributed among the junction lines and that each calling subscribers line has the possibility to connect iself to any one of the junction lines, an arrangement according to Figure 2 is nearly equivalent to an arrangement according to Figure 1 as regards its capability to receive and to take care of the traffic at the same trafiic frequency. The switching arrangements through which the call receivers are connected to the junction lines may be of arbitrary kind. They may, by way of eX- ample, consist of call finders allotted to the different call receivers the arrangement according to Figure 2 then offering the advantage over the arrangement according to Figure 1 that the call finders have a consider ably less capacity and consequently may be made smaller and cheaper.

To obtain a distribution as uniform as possible of the calls among the different junction lines or the call receivers respectively the system is preferably arranged in such a way that each call in known manner causes the starting of a plurality of call finders S. Then call distributors or starting distributors of known kind may be advantageously used which are started upon calls and, in different setting positions, successively start a number of call finders until a suitable number thereof have been started. The starting of said call finders is then controlled by the call distributor in such a manner that the latter in different setting positions starts call finders appertaining to difierent call receivers and, preferably in each setting position, starts a number of call finders appertaining to separate call receivers. In the arrange ment according to Figure 2, the call distributor, by way of example, in one position starts two call finders appertaining to the call receiver R and in next position two call finders appertaining to the call receiver R etc. The switching then proceeds in known manner so that the call finder first finding a calling line is engaged for the connection, other call finders then stopping. The appertaining call receiver may thereupon by means of its cord finder be connected to the junction line in question.

The switching time for connecting a subscribers line to a call receiver may be reduced if the switching arrangement instead is carried out in such a manner that a free call receiver in advance is connected to one of the appertaining junction lines being free at that time. Then only the call finder ap pertaining to said junction line will be started at the call whereas other junction lines and finders appertaining to the same call receiver which are not previously engaged, are

marked as engaged. The call receiver is then adapted to connect itself automatically to another junction line as soon as a connection has been completed. In an arrangement according to the invention the subscribers line will consequently be connected to the call receiver in the same moment as the appertaining call finder is connected to a subscribers line.

An important advantage of the invention resides therein that it offers a possibility to make use of simple electromagnetic relays for connecting the call receivers to the junction lines. This is of course also possible in the known arrangement according to Figure 1 but in the latter such an arrangement should become very uneconomical dependent upon the great number of relays then required. In an arrangement according to Figure 1 the number of relays required per junction line is thus equal to the number of call receivers whereas the arrangement according to Figure 2 only requires one relay per junction line. The invention renders thus possible the complete elimination of the call finders or register finders hitherto used. In practice, this does not however involve that said finders must be substituted by relays because already in known systems having finders each junction line is provided Iv with a relay to bring about the final connection with the call receiver. As said relays already provided for may be immediately utilized for comiecting up the call receivers in an arrangement according to the inven-' tion, said invention involves thus an immediate saving of said finders. At the same time the advantage of a momentary connection of the call receiver to the junction line is gained.

Figure 3 shows an embodiment of the invention in which a number of call receivers is common to two groups of junction lines G G corresponding to two subscribers groups each comprising five hundred subscribers. Each group G G comprises as before thirty-two junction lines F. It is assumed that a number of sixteen call receivers is adequate for the combined traffic in said two groups. The system is then arranged in such a manner that each call receiver may connect itself to a number of junction lines in both groups the different call receivers being distributed among the different junction lines in each special group in similar manner as in Figure 2. Then only two junction lines in each group will, how ever, be allotted to each call receiver. Otherwise the connection of the call receivers to the junction lines and the connection of the junction lines to the subscribers lines may take place in similar manner as described in connection with Figure 2.

Figure 4 shows an embodiment where thirty five call receivers are common to five groups G to G of junction lines which groups each corresponds to five hundred i. -e. the same number as the number of call receivers, Each call receiver may then be connected to only one junction line in each group in the manner shown on the drawings.

Figure 5 shows finally a modification of the arrangement according to Figure 4 according to which modification each call receiver has a possibility. to connect itself to two junction lines in each group, whereas at the same time each junction line is adapted to obtain connection to two different registers in the manner illustrated by the circles in the points of intersection between the difterent lines. Through the increased connection possibilities thereby offered the number of call receivers and the number of junction lines in each group may be reduced in relation to the arrangement according to Figure 4. In Figure 5 there are thus thirty two call receivers common to all the subscribers groups and each group comprises only thirty two junction lines.

Figure '6 shows an application of the invention in automatic telephone system having registers and power driven selectors which latter are of that kind the contact arm of which has a turning motion and a. radial motion in the same plane. The arrangement will be explained in other parts by the following description of the switching operation.

Upon calls the line relay LR is actuated in ordinary manner a circuit being then closed through a group relay LGR common to a roup of subscribers over the contact 1 of LR. The relay LGB closes in turn a test circuit through a starting relay SSR over the contact 2 of LGR. The relay SSE- is common to all the subscribers lines in the five hundred group in question. lVhen said relay is energized it closes a number of circuits 3 for a number of call finders S free for the time being. Said circuits extend over contacts of a call distributor SS which is started by the energization of its clutch magnet over a circuit 4. In the first moment only circuits 3 are closed for that number of call finders S which are connected to the contacts in the position taken up by the call distributor for the time being. The circuit 3 extends in the normal position of the sequence switch SOS of the call finder over a contact thereof whereby is ascertained that the sequence switch takes up its normal position. Said circuit further extends over a contact not shown in the group selector which is closed only in the eventuality of the group selector taking up its normal position. In the circuit 3 a relay'RS is included which now closes a circuit 6 including a relay RS which in turn closes a circuit 7 through the rotary magnet CVS of the finder said finder being then started to search that contact row in which the calling line is connected up. The relay RS then shifts the circuit 3 so that the relay RS instead is energized over a current path 8 including a cut off relay SSR The latter relay is so adjusted that it is actuated first when a certain number of relays RS are connected in parallel to the circuit 8. By this arrangement the number of started finders is limited as the relay SSH- upon being energized interrupts a circuit 4 and thereby brings the call distributor to stop. When the finder finds the contact row in question a cur rent path 9 including a test relay RS is closed which relay locks itself over its contact 10 and closes a current path 11 including a relay RS having a low resistance. Hereby the relay RS is shunted so that it is deenergized.

The starting relays RS for all call finders appertaining to the same register BEG are connected in parallel to the portion of the circuit 6 extending from the register. Through the connection of the relay RS into circuit in parallel with said portion of the circuit 6 the other call finders are marked as engaged as the appertaining relay RS then is unable to attract its armature. When the relay'RS was energized the circuit 7 was interrupted and the turning motion of the finder stopped. At the same time the sequence switch SOS was energized over'a current path 12 whereby it was brought to its third position. In said position a circuit 13 is now closed through the magnet CBS whereby the finder is started in radial direction. When the finder finds the calling subscribers line a new circuit 14: is closed for the test relay RS which is then ener ized and interrupts the circuit 13 whereby the selector is brought to stop. At the same time the clutch magnet of the sequence switch is energized over a current path 15 whereby the sequence switch is brought to its fourth position. In said position a circuit 16 is closed for that relay RS which connects the register REG to the junction line in question. As soon as the register has been connected into circuit a buzzer signal is sent in known manner to the calling subscriber which thereupon sends current impulses in known manner which actuate the relay BB in the register whereby the register is set according to the wanted number. l/Vhen the register has been set, the group selector is started thereby that a circuit is closed over the line branch La. The setting of the selector thereupon takes place in known manner by sending back impulses over the line branch Lb which impulses actuate a relay BB in the register. After the call con.- nection has been completed a circuit 17 is closed whereby the sequence switch is brought to the sixth position which is the speaking position. At the same time the register is 'disconnected which thereupon may be engaged to establish connections over other junction lines appertaining thereto. As long as the register operates the appertaining junction lines which are not engaged by a talking connection are marked as engaged 111 that the contact 18 in the circuit 6 is open which contact is closed only when the register takes up its normal position.

I claim:

1. An arrangement in telephone plants provided with calling lines, junction lines and call receivers, said calling lines being automatically connected to the junction lines and to the call receivers over the junction lines, such receivers comprising registers, operators positions and similar instruments. the call receivers belonging to a group of calling lines bein distributed among junction lines appertaining to the same line group in such a manner that each call receiver may be connected only to a limited number of said junction lines.

2. An arrangement as described in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call. receiver are distributed among different line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines.

3. An arrangement as described in claim 1, in which each junction line is adapted to be connected to only one call receiver whereas each call receiver may be connected to several of the junction lines belonging to the same line group.

4-. An arrangement as described in claim 1, in which each junction line is adapted to be connected to several of the call receivers belonging to the same line group.

5. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups 01" calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call receiver are distributed among different line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group.

6. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines in which the junction lines appertaining to the same call receiver are distributed among dififerent line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group, and in which when a call recelver 1s engaged by a unction l1ne the other junction lines belonging to the same call receiver are adapted to be,

in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each. individual group; and in which a call causes the starting of a plurality of call finders, and only such call finders are adapted o be started over which communication may be established with registers which are free for the time being.

8. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call receiver are distributed among diiierent line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group; and in which a call causes the starting of a plurality of call finders, and only such call finders are adapted to be started over which communication may be established with registers which are free for the time being; in which those call finders which are simultaneously started belong to different registers.

9. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call receiver are di stributed among different-line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines: and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group; and in which a call causes the starting of a pluralirelating to plants comprising a plurality of groups of calling lines each allotted to one group of junction lines; in which the unction lines appertaining to the same call receiver are distributed among different line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group; and in which a call causes the starting of a plurality of call finders, and only such call finders are adapted to be started over which communication may be established with registers which are free for the time being; the call finders being adapted to be started successively by means of a starting distributor which in diiierent setting positions starts call finders belonging to different registers; the starting distributor in each setting position being adapted to start call finders belonging to difierent registers.

11. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call receiver are distributed among different line groups in such a manner that the call re ceivers will be available for a plurality of groups of calling lines, and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group, and in which a call causes the starting of a plurality of call finders, and only such call finders are adapted to be started over which communication may be established with registers which are free for the time being, in which those call finders which are simultaneously started belong to different registers, and in which only one of the call finders appertaining to each individual register is started when a call is made.

12. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call receiver are distributed among difierent line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines, and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group; and in which a call causes the starting of a plurality of call finders, and only such call finders are adapted to be started which are free for the time being; in which those cal]. finders which are simultaneously started belong to different registers; and the register immediately after completed connection automatically connects itself to one of the appertaining junction lines free for the time beinm 13. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines, in which. the unction lines appertaining to the same call receiver are distributed among different line groups in such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group, and in which a call causes the starting of a plurality of callfinders, and only such call finders are adapted to be started which are free for the time being, in which those call finders which are simultaneously started belong to different registers, and the register immediately after completed connection automatically connects itself to one of the appertaining junction lines free for the time being, each register being provided with a finder for connecting the register to one of the appertaining junction lines.

14. An arrangement as claimed in claim 1, relating to plants comprising a plurality of groups of calling lines, each allotted to one group of junction lines; in which the junction lines appertaining to the same call re ceiver are distributed among different line groupsin such a manner that the call receivers will be available for a plurality of groups of calling lines; and in which the number of call receivers common to a plurality of line groups is substantially equal to the number of junction lines in each individual group; and in which a. call causes the starting of a plurality of call finders, and only such call finders are adapted to be started over which communication may be established with registers which are free for the time being; in which those call finders which are simultaneously started belong to difierent registers; and in which only one of the call finders appertaining to each individual register is started when a call is made, the registers being adapted to be connected to the junction lines by means of momentarily operating switching members.

15. In a telephone exchange system a main group of calling lines, a number of junction lines accessible in common to all lines of said main group and divided into a number of sub-groups, automatic switches adapted to connect a calling line with a junction line in any one of said sub-groups, a number of call registering devices individually allotted to difierent sub-groups of junction lines, and means forautomatieally connecting said call registering devices with any one of the appertaining junction lines.

16. In a telephone exchange system a plurality of main groups of calling lines, a corresponding number of main groups of junction lines the junction lines of each group being accessible in common to the corresponding group of calling lines and divided into a number of sub-groups, automatic switches adapted to connect a calling line with any one of the appertaining junction lines, a number of call registering devices accessible in common to a plurality of main groups of calling lines and individually allotted to difierent sub-groups of calling lines in each main group of such lines, and means for automatically connecting said call registering devices with a calling line.

17. A telephone system as claimed in claim 16, in which the call registering devices accessible in common to a plurality of main groups of calling lines are provided in a number equal to the number of junction lines in each main group.

18. In a telephone exchange system a main group of calling lines, a number of junction lines accessible in common to all lines of said main group and divided into a number of sub-groups, automatic switches adapted to connect a calling line with a junction line in any one of said sub-groups a number of call registering devices each of which is individually allotted to a different sub-group of junction lines, and relays for connecting each of said call registering devices in the appertaining junction lines.

19. In a telephone exchange system a main group of calling lines, a number of junction lines accessible in common to all lines of said main group and divided into a number of subgroups, call finders associated with said junction lines and adapted to connect a calling line with a junction line in any one of said sub-groups, a number of call registering devices individually allotted to difierent subgroups of junction lines, means for automatically connecting said call registering devices with any one of the appertaining junction lines, and means comprising a starting distributor for automatically starting a number of call finders in succession, said starting distributor being adapted in different setting positions to start call finders associated with different sub-groups of junction lines.

20. A telephone system as claimed in claim 19, in which the starting distributor is adapted in each setting position to start a plural ity of call finders associated wit different sub-groups of junction lines.

21. A telephone system as claimed in claim 19, in which the starting distributor is adapted to start only one call finder of each subgroup of junction lines.

In testimony whereof I am); my signature.

KNUT LARSSON. 

